It is known that oil deterioration and the combustion process within internal combustion engines can create the accumulation of carbon deposits, sometimes referred to as carbon packing, on surfaces of engine components, and negatively affect the performance of the component and engine. In fact, carbon packing on engine components can decrease fuel economy, increase undesirable emissions, and eventually lead to a loss in engine power. Specifically, carbon packing can occur on ring grooves defined by an engine piston and in which rings are positioned to seal the space between an annular side surface of the piston and a cylinder liner. The carbon packing on the ring grooves can alter the position of the rings, increasing the tension between the liner and the rings. In extreme cases, the piston can become stuck, potentially causing catastrophic engine failure.
Moreover, carbon packing on the annular surface of the engine piston can make contact with the cylinder liner. As the piston reciprocates, the rings seal the combustion area, during combustion, at the piston-liner area. Further, the rings move oil from the crankcase to the top of the piston-liner area, creating a thin surface of oil to lubricate the liner-ring motion. Carbon packing in the piston-liner area causes more oil to be moved into the combustion chamber than desired. The excess oil interferes with the combustion of the fuel, resulting in decreased fuel efficiency. Further, the excess oil in the combustion chamber contributes to even more carbon packing and to undesirable emissions.
Carbon deposits caused by oil can occur in engine components other than pistons. For instance, an oil cooler includes a bundle of tubes through which coolant passes. As heated oil passes over the tubes, the heated oil can form deposits that adhere to the coolant tubes. The deposits can decrease the life the of the tubes, and decrease the thermal transfer efficiency between the coolant and the passing oil.
Over the years, engineers have sought methods of limiting carbon packing and deposits without making major alterations to the engine. For instance, carbon-resistant coatings, such as the coating described in U.S. Pat. No. 5,771,873, issued to Potter et al., on Jun. 30, 1998, have been applied to surfaces of engine components adjacent to and/or within the combustion chamber. The Potter carbon-resistant coating is an amorphous hydrogenated carbon film coating that is believed to prevent carbon packing because the coating is supposedly chemically inert with respect to deposit formation chemistry. The amorphous hydrogenated carbon film coating is illustrated for use on surfaces of intake valve, exhaust valves, fuel injectors and pistons which are exposed to the combustion chamber. However, the amorphous hydrogenated carbon film coating is fragile, and may not be able to withstand the limited movement, or lashing, of the piston rings against the annular sides surface of the piston as the piston reciprocates. Thus, the amorphous hydrogenated carbon film coating is not suitable for certain engine components, such as the annular surface of the piston.
The present disclosure is directed at overcoming one or more of the problems set forth above.